Coordinate measuring method and device with a contact member and light detector

ABSTRACT

A method and device for sensing the presence and location of an object in a reference plane by directing light along a line perpendicular to the plane, defining a ring in that plane encircling said line of light, and sensing, by a change in the condition of the light, the presence of an object on the ring. In a first, non-contacting embodiment, light is directed along a line which is the axis of the ring and directed outwardly and focused at the ring. A circular detector coaxial with the light ring is positioned to sense intrusion onto that ring of an object, and by using a circular diode array detector, one can detect both the presence and location of that object on the ring. According to another contacting embodiment, a disc is placed in the reference plane with the light shining through an opening therein, the disc being movable in any direction in said reference plane. When an object touches the disc at any point and moves it, this changes the location of the aperture through which the light passes. This change is sensed to indicate an object on the ring.

This is a continuation of application Ser. No. 207,081 filed Nov. 14,1980, U.S. Pat. No. 4,453,082.

BACKGROUND OF THE INVENTION

This invention relates to a coordinate measuring method and apparatus,and in particular, it relates to such a device using optical sensingmeans.

Existing coordinate measuring machines utilize a mechanical probe knownas the Renishaw probe. However, the known probes are expensive, slow(because they must contact the surface or part being sensed), prone tobreakage (again, because they must contact the part being sensed) andinaccurate in certain applications.

In general, the problem with respect to a coordinate measuring machineis to move the mechanical arm, the encoded coordinates of which are usedto perform the measurement, and to move the probe into a position suchthat it can register against some feature of the part being sensed suchas a bore wall, a flange face, etc. To this end, a considerable numberof probes have been used heretofore, one example typified by that shownin U.S. Pat. No. 4,177,568. However, the standard probe in the industryfor measuring coordinates remains the Renishaw probe.

Hence, there exists a need for a coordinate measuring means whichovercomes the disadvantages present in previous coordinate measuringmachines.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and probedevice for coordinate measurements which uses optics and senses thepresence or the presence and location of an object by directing a lightalong a line perpendicular to the reference plane of measurement andsenses a change in the condition of that light.

In accordance with a first embodiment of the invention, a non-contactingmethod and coordinate measuring probe are provided. In this embodimentlight is directed along a line and then deflected outwardly into areference plane whereat it focuses on a circle in the reference plane. Acircular detector is so arranged that it senses whether any object hasinterrupted the ring defined by the focused circle of light. If thecircular detector is a circular diode array, then the device can sensenot only the presence of the object interrupting the light ring, butalso the precise location thereof.

In another embodiment, this one involving contact with the part beingsensed, light is also directed along a line perpendicular to a referenceplane. A circular disc is located in the plane with the light passingthrough a small opening in the center thereof. This disc is permitted tomove in any direction in said reference plane, and in operation if anyobject engages the disc and moves it, it moves the small opening off ofcenter, thereby changing the characteristics of the light shiningtherethrough. This change is sensed and indicates the presence of anobject on the ring defined by the periphery of the disc.

Hence, it is an object of the present invention to provide a new andimproved coordinate measuring device.

It is another object of this invention to provide a new and improvedmethod for coordinate measurement.

It is still another object of this invention to provide a new andimproved coordinate measuring method and device which employs opticalmeans.

It is another object of this invention to provide a new and improvedcoordinate measuring method and apparatus in which a ring is defined ina reference plane, light is directed along the axis of that ring, andthe change in condition of that light is used to sense the presence orboth the presence and location of an object intersecting the ring.

It is still another object of the present invention to provide a new andimproved optical coordinate measuring device and method which senses thepresence or the presence and location of an object in a reference planesolely through the use of optical means without contacting the object.

It is still another object of the present invention to provide a new andimproved coordinate measuring device and method using optical means andhaving a part which contacts the object being sensed, but which ishighly simplified relative to previous coordinate measuring machines.

These and other objects of the present invention will become apparentfrom the detailed description to follow, taken together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

There follows a detailed description of the preferred embodiments of thepresent invention which are to be read together with the accompanyingdrawings wherein:

FIG. 1 is a schematic view illustrating a first embodiment of thepresent invention.

FIG. 2(a) is a schematic view illustrating a second embodiment of thepresent invention and

FIGS. 2(b) is detail of FIGS. (2a)

FIGS. 3, 4a, 4b, 5, 6 and 7 illustrate other embodiments of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a first embodiment of the invention. In thisembodiment the light means defines a "ring" in space which has nophysical presence but which exists as an optically sensitive entity.When this ring, at any point in its 360° comes in contact with anobject, a signal is generated which represents the presence andlocation, i.e. the coordinate of that object on the ring. In commonlyowned copending application Ser. No. 15,792, now U.S. Pat. No. 4,305,661there is shown (in FIG. 17) an optical probe for detecting conditions onthe wall of a bore, and wherein light was directed along the bore andthen at a reference plane reflected outwardly to the inside wall of thebore. The present invention is an improvement of the device shown insaid pending application, specifically an improvement including meansfor defining a ring and sensing the presence and location of an objectintersecting that ring.

Referring to FIG. 1, a laser beam 10 emanating from the end of a waveguide fiber 11 (for example Nippon Sheet Glass Company "Selfoc LongLaser Guide", diameter 0.75 mm, length one meter). The laser beam, afterbeing focused and imaged in a collimated manner by lens 12 is reflectedby diverting mirror 13 down through a lens 14 and cylindrical glass tube15 onto an inverted parabolic or conical mirror 16 from which it isreflected and focused outwardly along a ring 17 located in a referenceplane perpendicular to the axis of the light beam through glass tube 15.

As shown in FIG. 1, one point P on the ring 17 happens to coincide witha wall of part 18. In this condition the device would sense the presenceof the wall 18 at point P.

Light at the point P is reflected upwardly and imaged by the same lens14 through which the light originally passed onto a detector ring 20.Detector ring 20 can be a solid ring or preferably a circular diodearray. In the case of a solid ring, the detector signal is fed to theamplifier 21, threshold discriminator 22 and the resulting trip signalis sent to the coordinate measuring machine by interface 25. The solidring senses the location of the light in the following manner.

If the part is indeed present at the point P, light reaches the solidring and a part present signal is detected. The co-ordinate location ofthe part is then determined by reading the xy location of the probe inspace from machine scales (not shown) well known in the art.

If the part is located to the left of point P in the drawing, the probeis moved to the left until the light is detected on the ring. At thistime, the scale data is "locked-up", or registered, even though themachine can keep moving ie. over travel.

It is noted again that point P can be anywhere 360° and is then thefirst such object point registered in a given movement. Use of thecircular array, however, allows other points to be measured as well asthe direction of contact.

If the detector ring is instead a circular photo diode array, the diodewould be scanned by a scanning circuit 21. The scanning would take placeat a rate of up to several hundred to a thousand scans per seconddepending on the light level and on the output of the array as analyzedby the threshold circuit 22. Threshold circuit 22 would look for "blips"indicative of contact with the part surface and when one appeared itslocation and the fact that it has appeared at a given monent would beindicated at the interface 25.

In the illustrated embodiment, the lens 14 is shown performing the dualfunctions of helping to collimate or focus the incoming laser beam andthen imaging the return light. Alternatively, the lens 14 could have anopening through the center thereof in which case it would serve nopurpose for the incoming light but would still serve to image the lightreturning from the part 18 to the detector ring. In any case, theselection of the lenses 12 and 14 plus the curvature of the mirror 16would all be chosen so as to form the focused light ring at a distance Ras desired.

The embodiment of FIG. 1 is subject to a number of different variations.For example, rather than utilizing a remote laser beam, one can have thelaser located in place of the fiber 11. Alternatively, a diode laser orconceivably an LED light could be placed in the cylindrical glass tube15 itself or at the position of the mirror 13.

The device illustrated and described above is totally responsive tointrusions onto the ring from any direction and has all the capabilityof normal coordinate probes with the exception that it cannot respond inthe vertical direction (as viewed in FIG. 1), at least in the embodimentas illustrated and described. However, this embodiment can be modifiedby additional optical or mechanical means to provide the verticalsensing. For example, if the entire sensor unit was mounted on astrainable diaphragm located in the plane of the detector ring or theplane of the lens 14 the strains in this diaphragm could indicate avertical or "Z" axis deflection. Of course if the device shown at FIG. 1were used in such a manner that the lower end of the probe would contacta surface, it would be desirable to put a ball contact at the end of theprobe rather than the flat edge as shown in FIG. 1.

As an alternative, rather than sense the returning light and deliveringthe same to elements 21, 22 and 25, given the flexibilities of imagetransmission through wave guide fibers, particularly when monochromaticlight is used, it is within the scope of this invention to transmit thereflected light from the ring back through the same fiber 11 or adifferent fiber to allow the sensing of the light ring image to beperformed at a remote location.

The embodiment of FIG. 1 would operate as follows. The laser beam 10would be directed from the laser down the axis of the probe devicethrough the cylindrical glass tube 15 where it would hit the invertedparabolic mirror 16 which could actually be a cone type mirror as wellas a parabolic mirror. The mirror would deflect the light outwardly andfocus it as a nominal radius R from the probe axis. This focusing effectwould occur for the full 360° around the said axis in what has beendefined as a reference plane perpendicular to that axis. The projectedring is approximately 0.001 inches wide or greater at its focus in the360° ring.

If an object now intrudes onto this ring 17 the light reflectedtherefrom is imaged by the lens 14 onto the detector ring 20. Thedetector ring is small enough in the radial direction that for only avery short time does light from the part 18 image at the detector,namely when that part is at point P on the ring 17. If the part 18 isoutside of the lens field no point will exist at all and if it is insideof the ring 17, the light will not image on the detector ring 20.

The light on the detector ring has a nominal value all the way around.There are two ways by which it can sense the reflected light from thering 17. First, the detector ring can be operated in such a fashion thatthe light actually intersects the detector ring. Given AC coupling, thiswill provide an instantaneous rise in the signal on the detector ringwhich can be sensed.

The other way to operate the detector ring is as follows. Two concentricdetector rings can be provided with a "hole" in the middle. In this casethe signal received from reflected part 18 will first rise and then dropas the part is at the null point, and then it will rise again on theother side. This can provide better signal processing since theinterruption can be detected as a minimum of intensity in a "trough" andthreshold is not intensity dependent. Some memory would be required,however, since one deliberately overshoots the null position, this beinghard to avoid in any event, given the inertia of the coordinatemeasuring device.

Whichever type of detector is used, the sensing of the part 18 which hasblocked some portion of the light ring can be determined and theaccuracy of this is determined by the sensitivity of the detector ring,the magnificational lens system, the fineness of the ring focus, etc.With a one to one imaging system as shown, the accuracy is in the levelof 0.001 inches or better in terms of raw resolution.

If a circular photo diode array is used, it can be scanned at a highrate. This provides a much stronger indication of actual contact withthe part 18, although it is limited to 40000 scans per second which isquite high. (Reticon 69 element array) A particular advantage of acircular diode array is that with it one can easily ascertain where inthe 360° ring the interruption has occurred. This data may or may not beapparent from any one contact point from the cartesian coordinate axisof the coordinating measuring device.

FIG. 2(a) and 2(b), collectively referred to as FIG. 2, illustrateanother embodiment of the present invention, namely a simplifiedembodiment including a means for contacting the part.

In FIG. 2 a lens 40 such as a Selfoc fiber lens has mounted at the lowerend thereof a disc 41, the disc being capable of movement in anydirection within its plane. The disc is circular and the outer peripherythereof defines the reference circle. The disc is held in place by aspring 44. It includes an aperture 42 in the center thereof. A light 43such as an LED light source passes through the aperture 42 and the lens40. When the disc 41 is centered such that the aperture 42 is alsocentered, the light from 43 passing through 42 at lens 40 is imaged bylens 46 onto a detector 48. This detection is sensed along line 49 atoutput circuitry 50.

If the disc is moved off of center by virtue of contact with a part suchas 52, the light shining through aperture 42 is no longer imaged by lens46 onto a detector 48, and this fact is recorded by the output circuitry50, thereby reflecting the fact that the ring originally defined by theperiphery of disc 41 has been interrupted by an object.

Although the invention has been described in considerable detail withrespect to preferred embodiments thereof, it will be apparent that theinvention is capable of numerous modifications and variations apparentto those skilled in the art, without departing from the spirit and scopeof the invention.

FIG. 3 illustrates another embodiment of the contacting invention shownin FIG. 2. In this case, however, it is not simply the presence of thesurface that is detected but its actual location within a very smallmeasuring range about the center axis of the probe. A much moresophisticated scanning detector is utilized to accomplish this purpose.

The second thing about the FIG. 3 application is that it illustrates a 3axis (x, y, z) measuring probe rather than simply a 2 axis xy probe asin FIG. 2.

Let us consider the figure. In this case, a ball contact is utilizedwhich upon contact can deflect in any of the three axes. This ballcontact 60 is free to move vertically up and down the z axis of shaft62. As before, a disk 61 with a center hole is utilized together with alight emitting diode or other light source, 63. It is noted that thelight source could be simply a mirror with a light or other reflectivesurface source remote in the probe housing 64. A suitable source canalso be remoted with fiber optics or whatever.

As in FIG. 2 xy movement of the ball is also possible of over a smallrange as well, moving the disk back and forth. It is noted that in thisparticular instance, the ball moves with the shaft 62 and the housing 64fixed. It is also however feasible to construct this with the ball fixedrigidly to the shaft in the z axis and with the shaft 62 and ball 61moving in unison in the z axis.

This however does not have the z axis sensitivity of the one shown aswill be described.

The lens in this case 65 is a selfoc rod lens with a very short focallength. It forms an image with the help of relay lens 70 onto matrixdiode array 71 which can scan in two axes. This is read out bymicrocomputer 74.

An additional construction detail is the optional breakaway mounts 75which allow the ball to hit causing the probe to overtravel and thenreturn to its original position. It is noted that if the probe is onlyused to establish the point of contact, its return to exactly the sameposition is not perse required, since it can be rezeroed instantly tothe new position, whatever it is.

One additional feature of this, also shared by the figure 2 device, isthat, unlike previous probes such as the Reneshaw "touchfire" probe,this device can actually take data on coordinates of a part such as thenose tip of a tool for example, without requiring the coordinatemeasuring machine to do all of the "hunt and peck" motions that arenormally required. This is because the image of the hole can be seenover a small range on the matrix array surface, and therefore thesurface of the ball tracked continuously by the sensor itself, at leastwithin this range.

Consider the inset figure showing a blown-up view of the matrix arraysurface 76. Image 77 is that of a image at the correct focus in the zaxis indicative of the furthermost extension of the ball in the z axis.It's a well focussed spot and, in this case however, is shown to be alsocontacting in the xy plane so as to move the spot from the nominalcenterline of the matrix array in both x and y at a 45° vector.

The spot 78 is much enlarged from that of 77 and is indicative of themost upward (and thus most out of focus) vertical travel of the ball inthe z axis. Scanning of the diameters of the spots gives the z axislocation. Naturally just a change in diameter indicates the presence ofthe surface or contact.

In the 78 spot case, it is seen that it is moved to the opposite sidealso at a vector of 45° in the xy plane. All of these spot sizes and xyvectors are obtainable from the matrix array using circuitry such asshown in varius copending applications by the author and others, such asNew Photo Detector Array Based Measurement Systems. Again the images 77and 78 are of the hole 61 in the disk at different z locations. The factthat the image changes in z is because the lens is rigidly mounted tothe shaft on which the disk moves vertically thereby changing the focusdrastically since it is a very short focal length lens 65.

The actual constructional details of the ball in terms of the way inwhich it slides up and down the shaft and also side to side is not shownhere for clarity. Any suitable means to accomplish reasonable freedom ofmovement in the 3 axes is suitable. Naturally such movements wouldnormally be elastic to allow them to return to original nominalposition. Magnetic and pneumatic forces can also be used for thispurpose.

FIG. 4 illustrates another non-contact embodiment of the invention. Asshown, a shaft 100 mounted to a housing 101 which is rotatable about thecenter of the shaft axis on bearings 102.

Within the shaft is a lens, in this case, a "Selfoc" rod lens 105, witha wide angle (eg. 55°) field of view. In the particular arrangementshown, a semi conducting diode laser, in this case, the new visible type110, illuminates distal end of the selfoc end with light via focuscollection lens 111 which is optional. The light emerging from the otherend of the rod lens is collected by auxilliary lens 115 and focussedonto the part surface 116 through the use of mirror 117. Generallyspeaking, the lens and mirror are enclosed by a housing at least on 3 oftheir 4 sides but in this case, only one side is shown closed forclarity.

Light 119 from the focal point on the surface 120 is collected again bythe front surface of the rod lens, since it is within the acceptanceangle of the lens. It is then imaged, in this case, by lens 130 at theother end onto a linear photo diode array, 131. It is noted that lens130 may also be central to the rod lens with the light brought in fromlaser 110 via beam splitter as will be shown in FIG. 4B.

As the part 116 moves closer to the probe thereby decreasing theincluded angle between the surface and the probe axis, the spot image140 moves on the diode array, for example to a new position 141. It isnoted that the exact direction of movement on 141 is a function of theprobe design and that lens, focal lengths, etc. chosen. The distancemoved on the diode array can be detected via output circuits 150 and theposition of the surface of 116 determined.

To ensure that a surface 360° can be obtained, the total probe housing101 and shafts area 100 and all are mounted so as to be rotatable toprovide a 360° sweep.

The triangulation principles are herein have been discussed at greatlength in a copending application entitled "Method and Apparatus forElectro-optically Determining the Dimension, Location and Attitude".

The light has gone down the same path and returned via the same path. Inthe FIG. 4B example, a somewhat similar arrangement with two differinglight-paths is illustrated. In this case, the light to illuminate thepart is brought in at an angle, in this case, being furnished by diodelaser 200 focussed by lens 201 into fiber 202 whose output is thenfocussed by lens 203 into spot image 204 on the surface of the part 205,which in this case is a cutting tool insert on a boring bar 206.

Light from the part is deviated by mirror 207 and collected by selfocrod lens 208 in housing 210. It is noted here too that the angular conereturn from the spot is easily within the range of the rod lens.

The output of the rod lens is in turn relayed by lens 215 and imagedonto detector array 220. 221 illustrates the spot image on the detectorarray which in turn can be scanned out. screen. A matrix diode arraywhich can scan in 2 axes can be used and its output is shown on the TVscreen 230 for illustration purposes. Normally, however, all spotpositional data is computed, with no visual presentation perse.

In this version, another type of illumination is also shown foradditional surface and feature identification. In this case a continuousor flashed lamp 240 is used to illuminate the end of a fiber bundle 250whose fibers indeed can circle the selfoc lens as well as lens and otherfiber 202 if desired. Light from bundle 250 also can hit mirror 207 andilluminate the part with general broad illumination rather than the spotprovided by lens 203.

Since the matrix array system can also form an image usin the broadillumination, this image is of the part surface itself and gray scaleform which can be digitized. Such an image is shown of the cutting toolinsert edge area 260 displayed on the screen 230.

The advantage of doing this is that analysis can indicate where theprobe is relative to any part and the range be found by thetriangulation system shown. In other words, the probe has multiplecapacities within it. Again, like the FIG. 4A version, to obtain a 360°scan, the whole probe has to be rotated.

FIG. 5 illustrates another non-contact version of the invention similarto FIG. 4B in certain respects while also being similar to FIG. 13 in acopending application "Method and Apparatus for Determining PhysicalCharacteristics of Object and Object Surfaces". Housing 290 is providedwith shaft 291 which is either transparent or at least has the endsection 292 transparent such that light can pass through it. Suitabletransparent members would be glass and plastic, for example.

Light inputs the system from diode laser or for that matter external gaslaser 300 focussed by lens 301 via beam splitter 302 into selfoc rodlens 303. Emerging light 304 from the rod lens is redirected andfocussed by paraboloid of revolution mirror 310 to provide a continuousannular ring spot on the surface which is represented by 320 on surface325, in this or a drilled hole. It is noted that since the probe iscloser to the surface of the hole S_(B), than the opposite surface `B`S_(T), the spot is further forward on S_(B) than S_(T).

In any case the selfoc rod lens through its wide aperture, collects thelight that has been projected onto the surface on the angular focussedring from all 360° at once and via lens 330, this light is focussedonto, in this case, a two axis scanning diode array such as a matrixdiode array 335. This diode array is read out by microcomputer analysissystem 336 and a typical trace is shown on screen 338.

Since the part surface is a cylindrical hole, a quasi circular ring isdetected. This ring is however shifted from the centerline by the sameamount as the probe was shifted in the hole thereby indicative of thefact that the probe is not coaxial with the hole. Naturally if thesurface was not round, neither would be the return imaged ring.

Obviously one other use of this is to find where a single portion of asurface is in space much as the FIG. 1 example. For example, supposeonly the section from A to B of this surface was present in one plane.In this case, only the point 339 representing the image of the lightring intersection with the surface AB would appear and this wouldindicate that we had indeed contacted a surface and it was the distanceaway represented by that image point from the probe axis. This isdesirable information that can be fed back to the coordinate axis of thecoordinate measuring machine or for that matter, machine tool on whichthis probe is located. The location of AB from the centerline of theprobe which in this case is a distance x, gives the answer as to wherethe surface is. In this case, the distance y is equal to zero because itlies on the x centerline of the probe.

Another version of this probe, similar to that of FIGS. 1 and 4 in manyrespects is shown in FIG. 6. It illustrates the use of both x and z axismeasurement simultaneously, using a matrix diode array (as opposed to acircular array which indicate presence of the surface only). Furtherillustrated is a axicon or torodial lens as opposed to a normal lens.All these features are not necessarily required together and can beutilized with the other embodiments as well where feasible.

As shown in the figure, a probe contains a hollow shaft 400 mounted to ahousing 401. In this case, light from a light source 402 (in this case ahalogen lamp, collimated by lens 403) hits mirror r404 which directs itdown the shaft. A paraboloid of revolution type mirror 410 redirects thelight and focusses it out forward of the end of the probe as shown toform an annular ring spot as was just described relative to FIG. 5.Since the annvollar ring is projected at an oblique angle to the probeaxis, its point of intersection with a part surface has both the zcomponent in the vertical axis of the probe, and an xy component as wellsince it extends 360° around the center or z axis of the probe.

In this case, the angular ring is shown hitting a part 420 at two pointson its surface, 421 and 422. Light is collected by axicon lens 425 whichforms an image onto matrix photodiode array 430 which is read out bymicrocomputer 440. In this particular lens case, however, at any onesection the lens simply acts like a simple cylinder lens, and thereforein actuality, it is a cylinder lens with a 360° symmetry. Therefore, theimages of the spots 421 and 422 stay separated, 421' being the image of421, 422' being the image of 422. Naturally any other kind of array isalso feasible for this but suitable processing circuitry to read it outin a circular fashion as is also desirable in FIG. 5 has been shown in acopending application entitled "New Photo Detector Array BasedMeasurement Systems".

The interesting thing about this is not only the novel components, butthe fact that we are actually seeing in 3 axes simultaneously. Forexample, where the surface part 420 where it is intersected by the pointof annulus 421 is facing purely in the z axis whereas the partintersected by the other side of the annulus making spot 422 is facingpurely in the y axis. Both of these zones are detected. Other thanobvious light intensity differences which would happen in thisparticular example, (ie. spot image 421' would in general be muchbrighter than that of 422' given the angles of incidence and collectionby lens 425), there is no real way to tell which direction the surfaceof the part lies 420 is. This can, however, be determined by moving theprobe on the coordinate axis of the coordinate measuring machine. Inother words, if the probe is moved vertically in the z axis, it isobvious that the position of image 421' will change greatly on the photodetector array but 422' will stay fixed. This immediately tells in whichdirection the respective surfaces are facing. Obviously, compounddirections require either compound probe movements or suitable signalvector processing.

The ambiguity of which way the direction of the surface faces is oftenremoved, because one knows the part that one is inspecting in generaland it is only the differences in where the surfaces lie relative towhere they're supposed to lie that matter. In other words, most surfacescan never be substantially out in which direction they point. Forexample, as the probe was moved toward the part in the z axis, one wouldknown that one was to pick up the 421 surface in the z axis and then atthat point slew to the right with the probe in order to pick up thesurface point 422. In this case, operation is simple and we have a true3 axis non-contact measuring probe.

FIG. 7 illustrates another embodiment of the invention this time withseparate light sources or fiber remoted ends thereof located down in theprobe. As shown, the probe body 600 contains a light source, in thiscase a 610 diode laser, imaged by lens 611 onto the part surface 612 (ifpresent). Similarly, diode laser 615 is imaged by lens 616 onto surface623 (if present) and diode laser 617 is imaged by lens 618 on to surface622 (if present). In this manner, 3 different axes are measuredsimultaneously.

A single lens 620 collects the light from a necessary included anglefrom all spots made with the surface 612 shown in all cases. Thiscollection is done via prism 630 which has reflecting faces 631 and 632as well as transmitting zone in the center to collect back the lightfrom the spot 629 produced by lens 618. In this case, an auxilliary lens648 for the center axis is utilized to make the images from thedifferent spots fall in the same area. All 3 spots are focused by lensonto the diode array to form images 612', 622' and 623' on the diodearray 640. Readout of these positions gives the answer for all threespots. Naturally, the probe can also be rotated about its axis to make a360° sweep.

As in FIG. 4B, auxilliary lighting can be provided as well in thisparticular example, in this case, by light source 650 which is shownilluminating surfaces 612 and 622 (all windows are not shown in this andother diagrams for clarity but it is noted that generally glass windowswould seal the probe from the outside). This light source 650 coulddesirably be flashed so it would not interfere with the light spotsproduced normally, but when a gray scale image of the surface wasdesired on the array, it could be used but have a brief instantaneoushigh peak value. For use in these cases, diode array 640 ideally wouldbe a matrix array which could scan the images of the surfaces in twoaxes.

While visible light is preferred, it is understood that the word `light`and `optical` in the context of this invention encompasses allelectro-magnetic radiation wavelengths X-ray to infra red.

It should also be noted that the detector 48 of FIG. 2 or detector 78 ofFIG. 3 may be an analog position sensing detector, such as the UDTSC-10. This detector gives x and y voltage signals proportional to thedeviation of the image spot such as 47 from the center of the detector.Using this detector 2 axis position information of the disc can bedetermined similar to that obtainable with the matrix array 71, but inanalog rather than digital form.

It is also noted that the disc 41 in FIG. 2 or 61 in FIG. 3, may be amember not necessarily round on its outside (eg. triangular) and notnecessarily with a hole used for disc position monitoring. For example,consider the use of reticle rather than a hole such as 55, in 4 pointcontact member 56 in FIG. 2. The x-y coordinates of the reticle could bemonitored easily with the matrix array 71 of FIG. 3. Indeed it would goout of focus with z changes, just as does the hole of disc 61 in FIG. 3too, and these could be monitored. Indeed tilts can be monitored if oneside of the reticle goes out of focus more than another.

I claim:
 1. A device for optically sensing the presence of an object ina plane perpendicular to a reference axis, said device comprising:a discdisposed in said plane and movable in all directions in said plane; andmeans for directing light along the reference axis; detector means fordetecting a reference condition of the light when the disc is the restposition thereof, and for detecting a different condition of the lightwhen the position of the disc is changed from said rest position bycontact with the object.
 2. A device according to claim 1, wherein saiddisc has a hole therethrough, said light passing through the hole andimaging on said detector means in said rest position.
 3. A deviceaccording to claim 1, including means for moving the disc along the axisto sense the location of objects in different planes on the axis.
 4. Adevice according to claim 1 wherein said detector means is furtherresponsive to the amount of movement of the disc along said referenceaxis.
 5. A device according to claim 1 wherein said detector means isfurther capable of detecting the magnitude and direction of saidmovement of said disc relative to said reference axis.
 6. A deviceaccording to claim 5 wherein said detector means is a photo detectorarray.
 7. An apparatus as claimed in claim 1 wherein said disc is partof a ball contact member and said apparatus includes means for mountingsaid ball contact member for movement in a direction orthogonal to saidplane.
 8. A device according to claim 5 wherein said detector is ananalog position sensing detector.
 9. A method for optically sensing theposition and location of an object in a plane perpendicular to areference axis, comprising:locating a disc, in said plane, which ismovable in all directions in said plane from a normal rest position,directing light along the axis across said plane, and monitoring thelight received by a light detector disposed such that said detectorsenses a reference condition of the light when said disc is in the restposition thereof and senses a different condition of the light when saiddisc is moved by contact with a said object.
 10. A method according toclaim 9 further incorporating the step of moving said reference axisuntil said object presence is determined and reading the position ofsaid axis to determine the coordinate location of said object.
 11. Amethod according to claim 10 wherein said object direction of contact isfurther determined.
 12. A method according to claim 9 further comprisingdetermining the coordinates of said object relative to said referenceaxis.
 13. A device for optically sensing the presence and location of anobject, said device comprisinga contact member moveable in at least twodimensions from a normal, rest position thereof; a light source; amatrix photodetector array; means for forming an image on saidphotodetector array of at least one point of said contact member withsaid contact member in the rest position thereof; and means fordetermining the presence of a said object in contact with said contactmember from a change of position of said image relative to saidphotodetector array and for determining the amount of movement of saidcontact member relative to the rest position thereof from the output ofsaid photodetector array to thereby determine the relative location ofthe said object.
 14. A device as claimed in claim 13 wherein saiddetermining means comprises further means for determining the positionof the said object in a direction orthogonal to the plane of said twodimensions.
 15. A device as claimed in claim 13 wherein said determiningmeans includes means for comparing the size of the image of the contactmember in a non-rest position thereof with the size of said image forthe rest position of said contact member so as to determine the relativeposition of said contact member in a direction orthogonal to the planeof said photodetector array.
 16. A device as claimed in claim 13 whereinsaid contact member comprises a ball contact and said light source islocated within said ball contact.